fix:修改样式

.cursor/rules/ui-and-sections.mdc

@@ -10,6 +10,7 @@ alwaysApply: false
 
 - `hero`～`system`：`.poetic-section`（宣纸/国风：`--paper`、`--ink`、`--red`、`--gold`）
 - `tech`～`contact`：`.tech-section`（深色科技：`--tech`、`--tech-card`、`--tech-line`）
+- 普通模式 `activeIndex >= tech` 时顶栏加 `is-tech-theme`；展控（`?mode=stage`）不加
 - 新增章节必须选对主题族；勿混用两套配色令牌
 
 ## 改章节

src/App.css

@@ -65,6 +65,36 @@ a {
   box-shadow: 0 1.125rem 4.375rem rgba(83, 42, 18, 0.14);
   backdrop-filter: blur(1rem);
   transform: translateX(-50%);
+  transition: background 0.35s ease, border-color 0.35s ease, box-shadow 0.35s ease;
+}
+
+.topbar.is-tech-theme {
+  border-color: rgba(201, 154, 69, 0.28);
+  background: rgba(8, 9, 15, 0.78);
+  box-shadow: 0 1.125rem 4.375rem rgba(0, 0, 0, 0.35);
+}
+
+.topbar.is-tech-theme .brand-lockup strong,
+.topbar.is-tech-theme .brand-lockup small {
+  color: #fff4df;
+  transition: color 0.35s ease;
+}
+
+.topbar.is-tech-theme .nav-links {
+  color: rgba(241, 217, 154, 0.82);
+  transition: color 0.35s ease;
+}
+
+.topbar.is-tech-theme .nav-links a:hover,
+.topbar.is-tech-theme .nav-cta:hover {
+  color: var(--gold-light);
+}
+
+.topbar.is-tech-theme .nav-cta {
+  border-color: rgba(201, 154, 69, 0.42);
+  color: var(--gold-light);
+  background: rgba(255, 244, 223, 0.06);
+  transition: color 0.35s ease, border-color 0.35s ease, background 0.35s ease, transform 0.2s ease;
 }
 
 .brand-lockup {

src/App.tsx

@@ -223,10 +223,12 @@ function App() {
   }, [autoPlay, isStageMode])
 
   const progress = ((activeIndex + 1) / sections.length) * 100
+  const techSectionIndex = sections.findIndex((s) => s.id === 'tech')
+  const isTechTopbar = !isStageMode && techSectionIndex >= 0 && activeIndex >= techSectionIndex
 
   return (
     <div className={isStageMode ? 'site is-stage' : 'site'}>
-      <header className="topbar">
+      <header className={isTechTopbar ? 'topbar is-tech-theme' : 'topbar'}>
         <a className="brand-lockup" href="#hero" onClick={() => goToSection(0)}>
           <img className="haoke-logo-img" src="/assets/haoke-logo.png" alt="杜康好客" />
           <span>